Three point anchor - The Saga Continues

if it all stretches the same then how does it create and unequalized load? it's all the same. this is ridiculous.

What?!?!

Oh god.

Eric Moss wrote:Anyway, does anybody know what DAV recommends for a three point anchor?

Well I don´t do much instructing these days so don´t bother to keep up with whatever the DAV recommend this week but for belays recommended is two bolts, most routes over here have equipped belays anyway so joining loads of pieces together doesn´t play a major role.
Sometimes it´s nescessary to arrange a masterpoint like rescue or top-anchors for abseiling especially in the UK where bolts aren´t so acceptable (for my personal climbing I never build a masterpoint). I´ve never seen a cordalette used in Europe and see no need for one, I teach this using a 160cm sling with a bowline on the bight like the DAV recommend:-

Three point

And more than three points you need a second sling.

4 point

As you will notice this is a simpler, cheaper, lighter, easier, more adaptable method than those huge f#cking knots you are messing about with.

Greg D wrote:I must have questioned your "authority" by questioning your statement "use the rope". Despite all your fancy quoting, you really said nothing and really missed my points, perhaps intentionally. Relevant to this discussion: anchors. Relevant to your comment: stock internet comment "use the rope".

No, patto pretty much explained it right. Stiffness is a function of spring rate, and length. If you hold length equal (when comparing rope to cord), spring rate is all that matters.

Greg D wrote:2 feet of 9.5 mm climbing rope (for example) doesn't have as much absorption as you may think. And it may not be much different than 7mm nylon

What you're both missing is any numbers to back up your claims. So let's look at a comparison. As a rope benchmark I picked a random 9.5mm rope (Edelrid Eagle Lite Pro 9.5). I'm comparing it to 7mm Blue Water nylon accessory cord.

I calculated effective spring constant for various loads based on information readily available (K = F/(dL/L) method). This gave me two points for the rope (Static load, and UIAA fall load), and three for the Acc cord (reported on Blue Water site)

Comparison Chart

From this, here's what I've concluded: (edited)

The cord is much stiffer than the rope.

If we call more elongation better, then the rope will have about twice the elongation as the cord for the same load when the cord is doubled.

When comparing to a single strand, the rope always has a lower spring constant, and will elongate further.

Thanks for the numbers Brian. So a single strand would perform even better.

Jim Titt wrote: ... (for my personal climbing I never build a masterpoint). I´ve never seen a cordalette used in Europe and see no need for one, I teach this using a 160cm sling with a bowline on the bight like the DAV recommend...

Jim, unless there are reasons why it would not be advisable to thread bights of additional cord loops or slings into the BoB knot as I showed on my pg1 post, it seems to me that that option is more flexible (ie, better able to accommodate any number of pros in pretty much any configuration) and no more complicated to install than what you propose here. Plus it maintains a single masterpoint pulling (as evenly as one cares to make it) on all the available pros, for those who prefer doing that rather than clipping two or more MPs together.

Greg D wrote:Thanks for the numbers Brian. So a single strand would perform even better.

Sorry, no, I got that wrong.

The rope is better by a factor of 2 vs a doubled strand (if we are calling more elongation at the same load better).

For a single strand, the rope always has a lower spring constant (which results in more elongation).

If we assume the curve for the cord is linear, then if it see's the same peak load as the rope, it elongates 18.4% (vs 29% for the rope). It's also close to failure at this point.

It'd be nice if we have some intermediate points on the rope to understand the shape of the curve (it isn't linear). But it's also fairly safe to say it's always under the cord.

Brian L. wrote:It'd be nice if we have some intermediate points on the rope to understand the shape of the curve (it isn't linear).

Yes, it would be nice, especially because one data point (the one obtained from the dynamic elongation of the rope) is from an experiment with a falling mass, while the other 4 are from static pull tests.

It's also difficult to extrapolate the behavior of two strands from that of one. Hooke's law predicts an increase in force by almost square root of two, but ropes with triple certification show much lower ratios between impact forces with two strands and impact forces with one strand.

Jim Titt wrote: Sometimes it´s nescessary to arrange a masterpoint like rescue or top-anchors for abseiling especially in the UK where bolts aren´t so acceptable (for my personal climbing I never build a masterpoint)... I teach this using a 160cm sling with a bowline on the bight like the DAV recommend:- And more than three points you need a second sling.

Jim, are these the bowline-on-bights that you mentioned?

Why BoB, and not some other knot?

Modified version of Jim Titt's photo

I have to know WHY ?? why so complicated ???? Just fucking tie in,,it's not that hard.

The more Bullshit that comes with anchoring systems, the more accidents. and more shit you have to carry.

When I look at the photo above I hear one word "epic" What the fuck is that ? Shit, by the time you did that, I'm halfway up the next pitch.

You wanna spend time bullshitting about this ..or maybe climb ? It's the anchors that matter most..NOT how you tie in to them.

Kent Richards wrote: Jim, are these the bowline-on-bights that you mentioned? Why BoB, and not some other knot?

It gives two layers of material where you clip in and you can untie it after any load.

Jim Titt wrote: As you will notice this is a simpler, cheaper, lighter, easier, more adaptable method than those huge f#cking knots you are messing about with.

That is your "simpler, lighter, easier" option...? You're normally fairly spot on but you missed by a mile here. That anchor is way too complicated and totally unnecessary. I also should not have to mention to you that tying knots in Dyneema drastically reduces the strength of the material (by as much as 50%) and you're triaxialy loading your master-point biner using a biner that is especially weakened by tri loading. That creation looks like something out of the Unbelievable Anchors series that Climbing Mag hosts.

The alpine equalette is a much better option:



Or just the "huge f#cking knot" standard anchor that anyone can setup in 10 seconds and climbers have been using since the beginning of the sport:

20 kN wrote: That is your "simpler, lighter, easier" option...? You're normally fairly spot on but you missed by a mile here. That anchor is way too complicated and totally unnecessary. I also should not have to mention to you that tying knots in Dyneema drastically reduces the strength of the material (by as much as 50%) and you're triaxialy loading your master-point biner using a biner that is especially weakened by tri loading. That creation looks like something out of the Unbelievable Anchors series that Climbing Mag hosts. The alpine equalette is a much better option: Or just the "huge f#cking knot" standard anchor that anyone can setup in 10 seconds and climbers have been using since the beginning of the sport:

The OP asked how the DAV build 3 point anchors, as a DAV instructor the first photo is how I build them. The subsequent one is showing how you can expand to multiple points.
Triaxial loading is irrelevant in this context.
The slings are nylon.
Your methods are for two-piece anchors, not what the OP asked for.

Very cool rigging, Jim. Thank you.

I've not seen the likes of it in any English-written book. Do you know of any particular resource where one might find this method?

Could you explain why triaxial loading is irrelevant here?

Thanks again.

Eric Moss wrote:Very cool rigging, Jim. Thank you. I've not seen the likes of it in any English-written book. Do you know of any particular resource where one might find this method? Could you explain why triaxial loading is irrelevant here? Thanks again.

Using a sling with a BoB is standard for the DAV and found everywhere in the newer literature, just clipping direct into the lowest piece is just a logical, simple, fast way to extend to 3 pieces. No idea about English literature, I don´t read too many books like that these days.
Triaxial loading has never been shown to have any effect on the small end of an HMS karabiner and anyway the normal maximum loading expected on a belay is 6kN which the karabiner would survive cross loaded. For rescue hauling where you more normally need more than three pieces we use two steel karabiners.

brenta wrote: Hooke's law predicts an increase in force by almost square root of two, but ropes with triple certification show much lower ratios between impact forces with two strands and impact forces with one strand.

Keep in mind that half ropes are tested with a different load mass than singles and twins, so you can't directly compare them.

Greg D wrote:I must have questioned your "authority" by questioning your statement "use the rope".

I never said that in this context. I said use DYNAMIC rope. There is a difference. You can readily carry a thin dynamic cordelette if energy absorption is your thing.

Greg D wrote:2 feet of 9.5 mm climbing rope (for example) doesn't have as much absorption as you may think.

Why do you suggest that? 2 feet of climb rope has plenty of ability to absorb the shock loads that 2 feet of climbing rope would allow. Unless you are taking factor 10 falls on 2 feet of climbing rope then your will be fine. (And yes, factor 10 falls are possible)

Greg D wrote:And it may not be much different than 7mm nylon despite how many "greater than" symbols you use.

Saying "may" and ignoring facts doesn't help your argument. Which is plainly wrong.

I have facts (though they weren't referenced), because I would have thought it to be plainly obvious that dynamic rope is stretchier than static rope. What I thought would be obvious and as was attempted to be explained was that a stretch object is still stretchy whether it is short or long. You fail to understand that.
(I could go on about the elastic modulus and stiffness but I wouldn't want to complicate things for you.

Greg D wrote:Any questions. Your quoting skills are quite cute BTW.

When you continue to include piles of misinformation in your posts I'll continue to pick them apart and make it clear.

patto wrote: I never said that in this context. I said use DYNAMIC rope. There is a difference. You can readily carry a thin dynamic cordelette if energy absorption is your thing. Why do you suggest that? 2 feet of climb rope has plenty of ability to absorb the shock loads that 2 feet of climbing rope would allow. Unless you are taking factor 10 falls on 2 feet of climbing rope then your will be fine. (And yes, factor 10 falls are possible) Saying "may" and ignoring facts doesn't help your argument. Which is plainly wrong. I have facts (though they weren't referenced), because I would have thought it to be plainly obvious that dynamic rope is stretchier than static rope. You fail to understand that. (I could go on about the elastic modulus and stiffness but I wouldn't want to complicate things for you. When you continue to include piles of misinformation in your posts I'll continue to pick them apart and make it clear.

You are so cute when you get mad, especially when you are arguing and I'm on the beach relaxing. I love how serious you are about things that are really minutia. Arguing about "may think".

patto wrote: What I thought would be obvious and as was attempted to be explained was that a stretch object is still stretchy whether it is short or long. .

So, 2 feet of climbing rope can absorb as much energy as 20 feet?

I need to get back to stretching my modulus.

Greg D wrote: You are so cute when you get mad

Mad? Cute? You are certainly creative in your taunts. How about we stick to talking about climbing hey?

Greg D wrote:So, 2 feet of climbing rope can absorb as much energy as 20 feet? I need to get back to stretching my modulus.

Not sure if you are genuinely stupid or just trolling... Either way no use continuing this...